An intended substance (hereinafter, which may be referred to as an “object substance” or an “object product”) can be produced in a multi-tubular reactor (or a so-called shell-and-tube type reactor) wherein a plurality of straight reaction tubes (having diameter of about few centimeters (cm)) are accommodated in a cylindrical shell so that the reaction tubes are located in parallel with the central axis of the shell. Herein, for example, a catalyst has been filled in the reaction tube, a raw material gas is supplied into the reaction tube, and the raw material gas is subjected to a reaction while the raw material gas flows in the reaction tube in one direction.
In the reaction of the raw material gas in such reaction tube, its reaction temperature is very important in order to efficiently provide the object substance. Therefore, in the multi-tubular reactor, the temperature of the reaction tube can be controlled so as to be in an appropriate reaction temperature. Herein, for example, a fused salt such as sodium nitrite and potassium nitrate (HTS: Heat Transfer Salt) is used as a heat transfer medium. The heat transfer medium is supplied and filled inside the shell (specifically, between the shell and the reaction tubes provided therein). The heat transfer medium flows in the shell. For example, in the exothermic reaction, the reaction-heat generated from the reaction is removed by the heat transfer medium. In the endothermic reaction, the heat required for the reaction is supplied from the heat transfer medium to the reaction tube in order to heat the raw material gas therein. Accordingly, the temperature of the reaction tube is controlled so as to be in an appropriate reaction temperature.
In order to efficiently carry out the removal or addition of the heat by the heat transfer medium, it is required that the heat transfer medium efficiently comes into contact with many reaction tubes. Therefore, conventionally, in order to improve the contacting efficiency between the heat transfer medium and the reaction tube, arrangement of the reaction tubes is adjusted, or a baffle board(s) (or a baffle(s)) is/are provided in the shell of the multi-tubular reactor in order to control the flow of the heat transfer medium. By the improvement of the contacting efficiency between the heat transfer medium and the reaction tube, the efficiency of the removal or addition of the heat from/to the reaction tube by the heat transfer medium can be improved (see non-patent literature 1).
However, the number of the reaction tubes to be located in the multi-tubular reactor is few thousands or tens of thousands when they are many. Herein, a number of the reaction tubes can be arranged each other in a distance of about few millimeters (mm). Therefore, even if the arrangement of the reaction tubes is adjusted, or a baffle board(s) is/are provided in the shell of the multi-tubular reactor, it is extremely difficult for all the reaction tubes to be improved regarding the contact-circumstance between the heat transfer medium and the reaction tubes. Therefore, there could be a reaction tube on which the removal or addition of the heat by the heat transfer medium cannot be efficiently carried out. Herein, in case of that there is a reaction tube having such deteriorated heat-removing efficiency, an extremely elevated temperature part (or a hot spot) may be formed on the reaction tube due to accumulation of the reaction-heat, etc. Alternatively, an extremely lowered temperature part (or a cold spot) may be formed due to insufficient heating. In case of such hot spot or cold spot is formed, it is not easy to appropriately carry out the reaction of the raw material gas, and therefore, problems may be arisen wherein production efficiency of the object substance is lowered. Accordingly, the multi-tubular reactor is necessarily controlled in order to prevent the formation of such hot spot or cold spot.
As an art preventing the formation of the hot spot or cold spot, for example, those detecting location(s) where the hotspot part may be formed by measuring temperature of the catalyst in the reaction tube, and the like, are disclosed (in patent literature 1).
Patent literature 1 discloses arts for measuring the temperature of the catalyst by providing reaction tube groups formed by a plurality of reaction tubes in a fixed bed multi-tubular reactor, and providing catalyst temperature measures to all of the reaction tube groups or a part of the reaction tubes thereof. Herein, it is disclosed that presence or absence of the hotspot part is monitored by the catalyst temperature measures attached to the reaction tube groups, and that a gas phase catalytic oxidation reaction can be operated stably with high efficiency by controlling the reaction based on the measured results (see patent literature 1: page 5, lines 43-46 of the description).
Furthermore, patent literature 1 poses problems, when the number of the reaction tubes is large, difference of the flow pattern of the heat transfer medium in the fixed-bed multi-tubular reactor tends to become larger so that the difference of the flow pattern causes a change in the heat transfer state on the reaction tube. Herein, it is also disclosed that the reaction tube groups provided with the catalyst temperature measures are allocated to the portions where the flow patterns of the heat transfer medium flowing outside the reaction tubes are different, and it is possible to understand the temperature in the fixed-bed multi-tubular reactor more precisely (patent literature 1, page 5, lines 23-38 in the description).
Herein, as it is described above, patent literature 1 discloses that the allocation of the reaction tube groups provided with the catalyst temperature measures to the portions where the flow patterns of the heat transfer medium are different, and therefore it is possible to understand the temperature in the fixed-bed multi-tubular reactor more precisely. However, there is no specific description with respect to any relation between the flow pattern and the location where the hotspot part can be formed.
Patent literature 1 discloses and explains on the assumption that the fixed bed multi-tubular reactor employs a partially cut circular baffle board(s) (e.g., D-cut baffle board(s), semicircular baffle board(s), etc.) as a baffle board. It is considered in view of the flow pattern of FIG. 5 of the patent literature 1 (see non-patent literature 1, page 405).
However, the partially-cut circular baffle board can be applied to only a small type multi-tubular reactor (having reaction tubes which number is less than 10000). When the partially-cut circular baffle board is applied to a large type multi-tubular reactor (having reaction tubes which number is no less than 10000), flow resistance of the heat transfer medium flowing in the shell would be increased. Therefore, it is a rare case where the partially-cut circular baffle board(s) is/are employed in a large type multi-tubular reactor. Whereas, there are many cases where a circular baffle board(s) (i.e., a disk-and-doughnut type baffle board(s)) is/are employed. In order to appropriately control the reaction in such large type multi-tubular reactor, it is difficult to presume how to measure the temperature of the reaction tube and where such measurement is to be carried out in view of the arts which are disclosed in the patent literature 1.